1. Field of the Invention
The present invention relates to a bridge apparatus and a network using the bridge apparatus. More particularly, the present invention relates to an address allocating technique to a bridge port of a bridge apparatus for connecting between networks in SONET (synchronous optical network)/SDH (synchronous digital hierarchy) network.
2. Description of the Related Art
Conventionally, in a bridge apparatus used in a LAN (Local Area Network), an address allocating method to a bridge port is used as shown in FIG. 1. Referring to FIG. 1, a network 200 is used to connect between LANs (Local Area Network) (not shown). Bridge apparatuses (#1 to #5) 2-1 to 2-5 are provided in the network 200, and each of the bride apparatus 2-1 to 2-5 has bridge ports. MAC (media access control) addresses (MAC1 to MAC9) are addresses peculiar to the network 200 (so-called local addresses), and are allocated to the bridge ports of the bridge apparatuses (#1 to #5) 2-1 to 2-5. In this case, one address is uniquely allocated to the bridge port. Also, the MAC address is defined in 48 bits.
Also, each of the bridge apparatuses 2-1 to 2-5 uses a filtering database (not shown) to determine from which of the bridge ports a frame received through one bridge port should be transmitted, i.e., to carry out a filtering process. In an initial stage, no data is registered on the filtering database. By carrying out the following operations, data are registered onto the filtering database. Generally, this operation is called a filtering database building operation or a learning operation.
FIG. 2 shows a configuration example of the filtering database of the bridge apparatus 2-5. Referring to FIG. 2, data of the bridge port is registered on the filtering database in correspondence to each of the MAC addresses (MAC1 to MAC9) in network 200. The filtering database building operation to the filtering database of the bridge apparatus 2-5 will be described with reference to FIGS. 1 and 2.
In the initial stage, when a frame is received from the bridge port with the address MAC1 of the bridge apparatus 2-2 by the bridge port P1 of itself, the bridge apparatus 2-5 refers to the filtering database to check from which of the bridge ports a frame should be transmitted. However, no data is now registered on the filtering database. For this reason, the bridge apparatus 2-5 outputs the frame to all the bridge ports of itself. Also, the bridge apparatus 2-5 registers the bridge port P1 in a port field of the filtering database corresponding to the address MAC1.
Next, when a frame is received from the bridge port with the address MAC2 of the bridge apparatus 2-2 by the bridge port P1 of itself, the bridge apparatus 2-5 outputs the frame to all the bridge ports of itself, as in the above case. Then, the bridge apparatus 2-5 registers the bridge port P1 in a port field of the filtering database corresponding to the address MAC2.
In this way, data of the bridge port is registered on the port field of the filtering database corresponding to each of the MAC addresses (MAC1 to MAC9). In this case, all the MAC addresses (MAC1 to MAC9) to which the frames possibly arrive in the network 200 need to be registered on the filtering database.
However, in the system for allocating the addresses to the bridge ports of the bridge apparatus used in the above-mentioned conventional network, each of the bridge apparatuses identifies a port based on the 48-bit in-network MAC address, and the filtering database is built through the learning process of the MAC address. Therefore, when the bridge function is applied to a large-scaled network such as SONET (synchronous optical network)/SDH (synchronous digital hierarchy) network, there would be a problem that the number of entries increases in accordance with the scale of the network.
In conjunction with the above description, a filtering system of MAC address is disclosed in Japanese Laid Open Patent application (JP-A-Heisei 5-344125). In this reference, when a frame is transferred from a transmission route 1 to a node 2, it is determined whether the address of the frame is a broadcasting MAC address, a group MAC address or an individual MAC address. When the address of the frame is the broadcasting MAC address or the group MAC address, a software filtering is carried out. In case of the individual MAC address, a hardware filtering is carried out. Because a reception frequency of the group MAC address and the broadcasting MAC address is low, influences of the software filtering process to the overall filtering performance is low. The increase of registers in the filtering circuit and complication of a comparing circuit are prevented.
Also, a multi-port relay apparatus is disclosed in Japanese Laid Open Patent application (JP-A-Heisei 9-307579). In this reference, a multi-port relay apparatus has a plurality of ports and relays a frame between the ports. A virtual LAN address is allocated to a network apparatus connected to the port and can replace with a MAC address. The virtual LAN address has a flag showing that the address is a local address of the MAC address, a flag showing that the address is the virtual LAN address, an identification number of a virtual LAN group to which the network apparatus belongs, an identification number of the multi-port relay apparatus with which the network apparatus is connected, and a termination network equipment identification number for specifying the network apparatus with the address.
Also, a switching hub module is disclosed in Japanese Laid Open Patent application (JP-A-Heisei 9-64899). In this reference, the switching hub is comprised of a plurality of ports connected with a network, port interface modules for these ports, a higher rank module provided for the port interface modules to communicate with a host, and a filtering database which learns a transmission source MAC address of a reception frame in correspondence to the port, and searches one port based on a transmission destination address of the reception frame. A virtual port is provided in the above interface module to communicate with the higher rank module. The learning process of the MAC address and the searching of the filtering database are carried out to the virtual port, like the other ports. A MAC frame is assembled by setting the MAC address allocated to the above higher rank module in a transmission source address field of a MAC header part of the frame. The MAC frame is transmitted to the virtual port of the above interface module.
Also, a connection apparatus between LANs is disclosed in Japanese Laid Open Patent application (JP-A-Heisei 10-32597). In this reference, a bridge module 12 learns a transmission source MAC address, a subnet address of a transmission source network layer and a reception port and registers on a bridge table. Also, the bridge module 12 refers to the bridge table to carries out a bridging operation to a transmission destination MAC address, a transmission destination network layer address. Before deleting entries of ARP table and the bridge table when the lifetime comes, ARP module 13 transmits a request and updates the ARP table and the bridge table based on an ARP reply packet.
Also, a switching hub with a virtual LAN function is disclosed in Japanese Laid Open Patent application (JP-A-Heisei 10-150459). In this reference, the switching hub has a plurality of ports, and a filtering table to register a MAC address of a terminal, the port connected with the terminal, and a virtual LAN group to which the terminal belongs. A plurality of regions are provided for the filtering table to store identification data of the virtual LAN. A virtual LAN group is specified in a combination of the identification data stored in each region.